Re: [PATCH v2] Base boot and runtime requirements - initial commit


atishp@...
 

On Fri, 2021-04-23 at 08:36 +0800, Abner Chang wrote:


Atish Patra <atish.patra@...> 於 2021年4月23日 週五 上午7:34寫道:
On Tue, 2021-04-20 at 17:51 +0530, Rahul Pathak wrote:
Initial changes for the Base Boot & Runtime requirements.
The sections which are currently in-progress are marked as TBD.
These changes can serve as the starting point and more
details/changes
can be done tailored for RISC-V.
This is the main patch, there are minor changes in the
contributors
file
and the changelog which are not relevant for now so I am not
sending
those.

Signed-off-by: Rahul Pathak <rpathak@...>
---
 riscv-platform-spec.adoc | 125
++++++++++++++++++++++++++++++++++++-
--
 1 file changed, 118 insertions(+), 7 deletions(-)

diff --git a/riscv-platform-spec.adoc b/riscv-platform-spec.adoc
index 5d3b9c3..601fb61 100644
--- a/riscv-platform-spec.adoc
+++ b/riscv-platform-spec.adoc
@@ -32,6 +32,36 @@ include::profiles.adoc[]
 // Linux-2022 Platform
 == Linux-2022 Platform
 
+=== Terminology
+[cols="1,2", width=80%, align="left", options="header"]
+|===
+|TERM      | DESCRIPTION
+|SBI       | Supervisor Binary Interface   
+|UEFI      | Unified Extensible Firmware Interface
+|ACPI      | Advanced Configuration and Power Interface
+|SMBIOS    | System Management Basic I/O System
+|DTS       | Devicetree source file   
+|DTB       | Devicetree binary
+|RVA22     | RISC-V Application 2022
+|RV32GC    | RISC-V 32-bit general purpose ISA described as
RV32IMAFDC.
+|RV64GC    | RISC-V 64-bit general purpose ISA described as
RV64IMAFDC.     
+|===
+
+
+=== Specifications
+[cols="1,2", width=80%, align="left", options="header"]
+|===
+|SPECIFICATION      | VERSION
+|link:
https://uefi.org/sites/default/files/resources/UEFI_Spec_2_9_2021_03_18.pdf[UEFI
 Specification]         | v2.9   
+|link:
https://github.com/devicetree-org/devicetree-specification/releases/tag/v0.3[Devicetree
 Specification]  | v0.3
+|link:
https://github.com/riscv/riscv-sbi-doc/blob/master/riscv-sbi.adoc[SBI
 Specification]                    | v0.3-rc0
+|link:[RVA22
Specification]                                                     
  
                            | TBD
+|link:https://arm-software.github.io/ebbr/[EBBR Specification]    
  
                                          | v2.0.0-pre1   
+|link:
https://uefi.org/sites/default/files/resources/ACPI_Spec_6_4_Jan22.pdf[ACPI
 Specification]              | v6.4
+|link:
https://www.dmtf.org/sites/default/files/standards/documents/DSP0134_3.4.0.pdf[SMBIOS
 Specification]    | v3.4.0
+|link:[Platform
Policy]                                                            
  
                         | TBD
+|===
+
 // Base feature set for Linux-2022 Platform
 === Base
 ==== Architecture
@@ -57,14 +87,95 @@ include::profiles.adoc[]
 * Timers
 * Watchdog Timers
 
-==== Boot Process
-* Firmware
-* Boot-Loader
-* Discovery Mechanisms
+==== Boot and Runtime Requirements
+- The base specification defines the interface between the
firmware
and the
+operating system suitable for the RISC-V platforms with rich
operating
+systems.
+- These requirements specifies the required boot and runtime
services, device
+discovery mechanism, etc.
+- The requirements are operating system agnostic, specific
firmware/bootloader
+implementation agnostic.
+- The base boot specification depends on the RVA22 profile and
all
requirements
+from the RVA22 profile must be implemented.
+- The base runtime specification depends on the RISC-V SBI
specification and
+all requirements from the SBI spec must be implemented.
This statement is bit ambiguous given that individual SBI section
says
legacy ones must not be implemented.


+- Any RV32GC or RV64GC system with Machine, Supervisor and User
Mode
can comply
+with the base specification. 
Should we reword something like this,

Any platform seeking compliance with the base specification, must
implement all three privilege modes i.e. M/S/U mode.

Hypervisor Extension is optional.
Do we need to state this explicitly? I am just trying see if we can
avoid any statements with optional word as per previous
discussions.   

Any platform implementing M/S/U complies with base. If they
implement H
extension on top of that but not aimed for server extension
compliance,
they are still compliant with base specification.

+_**Will be defined in this spec if the RVA22 spec does not
mention
it.**_
+- For the generic mandatory requirements this base specification
will refer to
+the EBBR Specification. Any deviation from the EBBR will be
explicitly
+mentioned in the requirements.
Just for clarification, RISC-V specific content in EBBR is not
merged
yet. The last version of the patch can be found here.

https://www.mail-archive.com/boot-architecture@lists.linaro.org/msg01545.html
This may fix my concern in the previous reply.
Atish, do you mean we will have RISC-V elements in EBBR spec. That is
EBBR would be a spec for embedded systems on different archs?
Yes. Additional clarification for everybody: EBBR is meant for embedded
systems as in embedded Linux. The embedded 2022 in RISC-V platform spec
is aimed towards the bare metal/micro-controller platforms.

I think we need to fix the naming sooner than we thought :)

If the above is true, then I have no problem with referring to EBBR
in this spec.

Abner
 


I will try to revise/rebase it on the latest EBBR specification.

+- Specifications followed are mentioned in the 
+<<Specifications,Specification Section>>
+- For more on scope of MANDATORY, DEPRECATED, COMPATIBILITY
refer
Platform
+Policy Specification.
+
+
+===== Firmware
+- UEFI Platform must meet RISC-V Platform requirements on
calling
conventions,
+ABI support specific to RISC-V. Refer Chapter - 2.3.7 RISC-V
Platforms of UEFI
+specification.
+- For compliance with base specification platform must implement
+link:https://arm-software.github.io/ebbr/#required-elements[EBBR -

UEFI Required Elements],
+link: 
https://arm-software.github.io/ebbr/#required-platform-specific-elements[EBBR
 - UEFI Platform Specific Elements]
+and support the following
+link: 
https://arm-software.github.io/ebbr/#required-global-variables[EBBR
 -
Global Variables].
+
+====== Block Device Partition Format
+- Firmware must implement the support for GPT Partitioning and
meet
the
+requirements as per the
+link:https://arm-software.github.io/ebbr/#firmware-storage[EBBR Fi
rm
ware Storage].
+
+===== Boot Services
+- Base specification compliant firmware must implement all UEFI
functions
+marked as EFI_BOOT_SERVICES.
+
Implementing all EFI_BOOT_SERVICES shouldn't be mandatory. It can
reworded similar to what EBBR has done.

All functions defined as boot services must exist. Methods for
unsupported or unimplemented behavior must return an appropriate
error
code.


+====== Startup Protocol
+- UEFI firmware could be executed in either Machine mode or
Supervisor mode
+during the entire POST, according to the hart capability and the
platform
+design. For firmware privilege mode requirements, mode switch
and
the handover
+of control to S-Mode refer UEFI chapter 2.3.7 RISC-V Platforms.
+- Before yielding control to S-Mode stage, firmware must
configure
the M-Mode
+state. Refer the RISC-V SBI specification for details.
Are we talking about only CSR configuration or all other
implmentation
expectations from M-mode such as interrupt/exception delegation,
misaligned/missing CSR emulation, PMP configuration ?

+- If the Hypervisor Extension is implemented. **TBD**.
+
+
+====== Memory Map
+- UEFI environment must provide a system memory map and meet the
requirements
+for link:https://arm-software.github.io/ebbr/#memory-map[EBBR -
Memory Map].
+
In addition to this, should we standardize a start address (i.e.
0x80000000)


+===== Boot-Loader
+**TBD**
+
+===== Discovery Mechanisms
+- The base specification mandates the use of Devicetree for
system
description.
+- System must meet link: 
https://arm-software.github.io/ebbr/#devicetree[EBBR - Devicetree
requirements]
+to comply with this base specification. Also refer Devicetree
tables
section
+in chapter - 4.6 EFI Configuration Table & Properties Table of
UEFI
+specification.
 
-==== Runtime services
-* SBI
-* UEFI
+===== Runtime Services
+====== SBI
+- Firmware must implement the runtime services/extensions
specified
by the
+RISC-V SBI Specification.
I think we can just mandate SBI v0.3. The base specification may
not
have to implement all the SBI extensions in future.

+- Wherever applicable firmware must implement UEFI interfaces
over
similar
+interfaces and services present in the SBI specification. For
example, UEFI
+runtime services must implement ResetSystem() via SBI Reset
extension.
+- Legacy Extensions from the SBI Specification are deprecated
and
must not be
+implemented.
+
+====== UEFI
+- Firmware must conform to the
+link:
https://arm-software.github.io/ebbr/#uefi-runtime-services[EBBR
 - UEFI EFI_RUNTIME_SERVICES requirements].
+- Firmware must meet the requirements for
+link: 
https://arm-software.github.io/ebbr/#runtime-device-mappings[EBBR -

Runtime Device Mappings]
+to avoid conflict between the firmware and OS when accessing the
mapped
+devices.
+- Compliant UEFI runtime environment must meet the requirements
for
the
+link: 
https://arm-software.github.io/ebbr/#runtime-variable-access[EBBR -

Runtime Variable Access].
+- Compliant implementation must meet the Realtime Clock
requirements
+link:https://arm-software.github.io/ebbr/#real-time-clock-rtc[EBBR
 -
UEFI RTC interface]
+if RTC is present in the system.
 
 // Server extension for Linux-2022 Platform
 === Server Extension
--
Regards,
Atish

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